1. Field of the Invention
The present invention relates to a power tool including a housing, an output member projecting from the housing, a drive located in the housing for rotating the output member about an axis, and a slip clutch for transmitting torque from the drive to the output member. The slip clutch has a plurality of clutch elements retained against rotation relative to the housing, a control element having a respective plurality of counter-clutch elements cooperating with the plurality of clutch elements, and a plurality of separate spring elements for preloading the clutch elements against the counter-clutch elements of the control element. Thereby, the control element is retained against rotation upon application of the torque thereto until threshold of the torque is reached. A rotatable adjustment element adjusts the preload applied by the spring elements.
2. Description of the Prior Art
In the power tools of the type described above, at a certain resistance torque applied to the output member, transmission of a driving torque, which is produced by the tool drive, to the output member is interrupted in order to prevent any damage. In this power tool, the use of a plurality of separate spring elements insures retaining of a uniform spring characteristic during the service life of the tool to a most possible extent. Thereby, the torque transmission, at a predetermined threshold of the torque, is always interrupted at substantially the same actual torque during the service life of the power tool.
European Patent EP 0 613 758 B1 discloses a power tool with a clutch mechanism with a plurality of helical springs the first ends of which applies pressure to a spherical clutch element, and the second ends of which are supported against a clutch ring. For adjusting the preload against the clutch element, the axial position of the clutch ring is adjusted by rotating the clutch ring. The helical springs project in bores formed in the housing and are associated with respective clutch elements.
The drawback of the known clutch mechanism consists in the large number of separate elements, which increases manufacturing and assembly costs.
Accordingly, an object of the present invention is to provide a power tool in which the drawbacks of the known power tool is eliminated.
Another object of the present invention is to provide a clutch for a power tool and having a stable spring characteristic at a simple construction of the clutch.